Extensible coupling for well pipes

ABSTRACT

An extensible coupling for use in well pipe strings, particularly rotary drill strings, to permit relative longitudinal, nonrotative movement between sections of the pipe string by employing a spline connection in which the male spline member is removably mounted in the wall of the outer coupling member.

United States Patent [111 3,630,551

[72] Inventor Cicero C. Brown [56] References Cit d ggfizlsturbrldge Drive, Houston, Tex. UNITED STATES PATENTS 3,504,936 4/1970 Brown et al 285/330 X Eff; 53: 1? 1970 2,444,922 7/1948 Deetman 287/52.05 [45] Paemed Dec 28l971 3,356,393 12/1967 Casanov.. 287/5208 3,319,726 5/1967 Brown 166/.5 X

' Primary Examiner-Andrew V. Kundrat [54] EXTENSIBLE COUPLING FOR WELL PIPES Auomy R Warn 3 Clalms, 4 Drawing Fly.

[52] U.S. Cl ABSTRACT: An extensible p g for use in we" p p [5 n in CI F16 zsioo strings, particularly rotary drill strings, to permit relative lon- [so] ne'ld 285/302 gitudinal, nonrotative movement between sections of the pipe 330 no 202 64/2} 287/52 05 53 LK 58 string by employing a spline connection in which the male S 08 spline member is removably mounted in the wall of the outer coupling member.

PATENTED 0E28 19?! A TTORNE) EXTENSIBLE COUPLING FOR WELL PIPES In drilling wells by the conventional rotary method, particularly from a floating drilling platform, the platform will be subjected to vertical movements in response to the passage of waves over the surface of the water body on which it is afloat. This necessarily produces a corresponding up and down movement of the drill pipe string, which is a serious hindrance to the drilling operation, particularly to maintenance of a constant weight on the drill bit during the drilling operation, since upward movement tends to pull the bit and drill collars off bottom while downward movement may tend to apply undue downward pressure on the drill string and the bit.

Various types of extensible couplings, commonly called slack joints," or drilling splines," have heretofore been employed to overcome this difficulty by providing an extensible coupling in the drill pipe string which will allow for the vertical movements of the floating platform while maintaining the bit in constant contact with the bottom of the well and at the same time maintaining rotation of the drill string necessary to turn the drill bit. Such conventional joints employ various forms of splined connections between telescoping members of the coupling to accommodate the longitudinal movement which occurs. However, such conventional couplings are subject to very severe wear and to unbalanced pressure forces such that they must be replaced frequently and may, in some instances, become broken by reason of the extensive wear thereon. Moreover, many of the conventional couplings are made relatively complex in an effort to meet the conditions encountered and their'complicated construction necessarily creates problems in maintaining the parts in efficient working condition under the severe loads frequently imposed thereon.

Furthermore, under the severe operating conditions commonly encountered conventional couplings are subject to leakage between the coupling members which may permit circulating drilling fluid to bypass the drill bit, with a consequent loss of drilling efficiency.

A form of coupling designed to successfully meet the aforedescribed condition has heretofore been disclosed and patented by the present applicant and James D. Mott in US. Pat. No. 3,504,936, issued Apr. 7, 1970. The coupling therein disclosed contemplated a structure employing tubular telescoping members connected for longitudinal relative nonrotative movement by a spline connection comprising elongate male splines on the outer member received in female spline grooves on the inner member and having antifriction bearings arranged therebetween to provide relatively frictionfree movement between the coupling members. A highly effective sealing unit was also provided between the members.

In this earlier form of coupling, the male splines were welded into place in the outer coupling members after the hearings were in place between the spline members. The male spline thus became an integral part of the outer coupling member. This construction has been found to have certain dis advantages, primarily because of limitation on the ability to replace the bearings readily when they became worn. It was also found, particularly where the bearings were ball bearings, that due to the torsional stresses to which the coupling was exposed, the wearing in the bearing races was uneven, a greater degree of wear occuring at one end than at the other. The nature of this wear was such, however, that it was found, after a period of use, that if the male splines could be turned end-forend relative to the female splines, the races in the coupling would be restored substantially to their original form and efficiency, thereby greatly extending the useful life of the coupling. Due, however, to the welded construction theretofore employed, it was found to be generally impractical to effect the desired reversal of the male splines without greatly weakening or even destroying the coupling.

The present invention, therefore, contemplates an improvement in the coupling construction wherein the male splines are removably mountable in suitable openings in the outer coupling member so that they can be removed at will, turned end-for-end and reinstalled to restore the coupling substantially to its original efficiency and extend the life of the coupling.

Other and more specific objects and advantages of this invention will become more readily apparent from the following detailed description when read in conjunction with the accompanying drawings which illustrates a useful embodiment in accordance with this invention.

In the drawing:

FIG. I is a longitudinal quarter-sectional view of the exemplary coupling with the coupling members in their relatively contracted positions;

FIG. 2 is a cross-sectional view taken along line 22 of FIG. 1;

FIG. 3 is an exterior view in elevation of one of the male spline members; and

FIG. 4 is a fragmentary sectional view, on a somewhat enlarged scale, taken along line 44 of FIG. 2.

Referring to the drawing, the coupling comprises the tubular male member, designated generally by the numeral 10, and the tubular female member, designated generally by the numeral II, adapted to telescopically receive the male member for limited relative longitudinal movement.

The male member is composed of an upper section [2, an intermediate section 12a, and a lower section 13 of smaller external diameter than the upper and intermediate sections. A threaded pin-and-box connection 14a connects the upper end of section 12a to the lower end of section 12, and a reducer coupling 14 connects the lower end of section 12a to the upper end of section 13. The upper end of section 12 carries the enlarged internally threaded box 15 for connecting the male member to pipe string P.

Female member 11 is likewise made up of a plurality of coaxial interconnected sections, including an upper section 17, an intermediate section and a lower section 18. A threaded pin-and-box connection 19 connects the upper end of intermediate section 17a to the lower end of upper section 17. A threaded pin-and-box connection 18a connects the lower end of section 17a to the upper end of lower section 18. The lower end of the latter is internally threaded at 18b to threadedly receive the upper end of an adapter collar 20 by which female member 11 is connected to a subadjacent section of pipe P (not shown). The inner end of adapter 20 forms an upwardly facing annular shoulder 21 in the lower end of the bore of section 18 and serves purposes to be described hereinafter.

The upper end of upper section 17 is counterbored to define the chamber 50 and is internally threaded at its upper end to receive the externally threaded end of an annular bushing 51 which slidably surrounds the upper end of section 12. A sealed piston 52 is slidably disposed about section 12 inside chamber 50 and is longitudinally movable therein between limiting abutments formed by the inner end of bushing 51 and the bottom of chamber 50.

Intermediate section 17a is provided with at least two, angularly spaced, generally rectangular radial openings 21 adapted to receive correspondingly shaped male splines 22, each of which is mounted in the innerface of a plate 23 provided with bolt flanges 24-24 extending laterally from its opposite side edges and bold flanges 2525 extending longitudinally from its opposite ends. The outer end of each opening 21 is countersunk about its periphery to a depth to receive the several flanges 24 and 25 in flush relation to the exterior of the 'sections comprising outer coupling member 11. Cap screws 26 are disposed to extend through the several flanges to strongly but removably secure plate 23 and the male spline thereon in openings 21.

Male splines 22 project into the bore of intermediate section 17a (FIG. 2) and each spline has parallel arcuate recesses 27 along its side edges which are joined at their opposite ends by convex arcuate end portion 28 cut across the body of the spline (FIGS. 2 and 4).

The male splines project into longitudinal spline slots 29 provided in the outer surface of intermediate male section 120. Spline slots 29 are defined by parallel sidewalls 30 and upper and lower end walls 30a and 30b, respectively. The junctions between the sidewalls 30 and end walls 30a and 30b with the bottoms of slots 29 are made arcuate to define ball races 31 complementing the arcuate configuration of recesses 27. The length of slots 29 is made sufficiently greater than the length of male splines 22 to permit the desired extent of relative longitudinal movement between the coupling members, which will be limited by the abutment of end walls 30a and 30b with the related ends of male splines 22.

The width of slots 29 is made substantially greater than the width of splines 22 to provide a space 32 which forms the bearing race therebetween, defined in part by the complementary arcuate recesses 27 and 31, and including upper and lower race portions 28a and 28b, respectively.

Bearing race 32 is filled with a plurality of bearing balls 33 arranged to be in free continuous rolling engagement with one another, whereby they can readily accommodate themselves to relative longitudinal movements between the coupling members and also to relative lateral shifting movements between the coupling members and more importantly, to any relative twisting movements between the coupling members resulting from torsional forces therebetween. This freedom of movement will effectively reduce friction and prevent any binding between the coupling members during relative extension and retraction thereof.

In construction of the device, in order to accommodate the small helical configuration which may develop in the elongate splines under the torsional forces to which they are subjected in operation, the parts forming the ball races will first be milled to practically a metal-to-metal fit with the balls. Then the balls are installed and the coupling assembled. Thereupon the splines will be worked through their limits while applying the amount of torque anticipated for a normal operation. This construction and preoperation produces a twofold advantage: the ball races are work-hardened to an exact fit and a helix of the proper shape will be worn into the races, thereby reducing friction in operation and resulting in a longer life for the tool.

To further reduce friction in the coupling, the interior of the coupling between the male and female members is sealed-off at points above and below the splines to form a chamber b. The seals comprise sealed piston 52 at one end, and at the other end a seal ring which is seated in the exterior of coupling 14 to seal with the interior of section l8.

The present modification also includes a seal assembly, designated generally by the numeral 35, which is substantially identical with seal assembly 30 of the embodiment described in the aforementioned US. Pat. No. 3,504,936 and will not, therefore, be described in detail, except to note that its positioned in the annular space 36 between sections 13 and 18 and held therein between shoulder 21 and an adjacent shoulder.

Operation of the coupling will be evident from the foregoing description of the device but it may be pointed out that as the coupling members are relatively extended and retracted, the antifriction bearings between the spline elements will permit relatively frictionless movement under the various stresses to which the pipe string may be subjected. At the same time, the seal assembly will assure against leakage of fluid into and from the pipe string.

By providing spline plates 23 of symmetrical form and detachable construction, the plates and splines carried thereon can be readily removed and reattached whenever required to replace the bearings and, as noted previously, may be turned end-for-end to extend the useful life of the coupling.

It will be understood that various changes and modifications may be made in the details of the illustrative embodiment within the scope of the appended claims but without departing from the spirit of this invention.

What I claim and desire to secure by Letters Patent is:

1. An extensible coupling for well pipe strings, comprising:

a. telescopically engaged inner and outer tubular members;

b. means carried by the outer ends of the members for connecting them to adjacent sections of a pipe string;

c. pairs of male and female spline elements cooperably disposed respectively on the outer and inner members to form a nonrotatin longitudinally slidable connection between said mem ers and to define a continuous annular bearing race therebetween;

d. a pair of angularly spaced, elongate, generally rectangular openings in the wall of said outer member registering with said female spline elements and adapted to removably receive said male spline elements;

e. flange elements extending from the sides and ends of said male spline elements to overlie the related edges of said openings;

f. fastening means releasably securing said flanges to said outer member about said openings; and

g. bearing means operably disposed in said bearing race.

2. An extensible coupling according to claim 1 including a sealing assembly positioned in sealing relation between said coupling members below said slidable connection.

3. An extensible coupling for well pipe strings comprising:

a. telescopically engaged inner and outer tubular members;

b. means carried by the outer ends of the members for connecting them to adjacent sections of a pipe string;

c. an elongate, generally rectangular recess in the exterior of said inner member defining a female spline;

d. an elongate, generally rectangular opening in the wall of the outer member registering with said recess;

e. a closure plate removably mounted in said opening and corresponding in shape thereto;

means for releasably securing said plate about said openg. an elongate male spline carried on the inner face of said closure plate to be nonrotatively slidably received in said recess;

h. a bearing race defined between the sides of said male spline and the adjacent walls of said recess; and

i. ball bearing means operably disposed in said bearing race; said closure plate having bolt flanges symmetrically disposed along its side edges and opposite ends to permit turning said male splines end-for-end in said openings while maintaining said defined bearing race between said spline element. 

1. An extensible coupling for well pipe strings, comprising: a. telescopically engaged inner and outer tubular members; b. means carried by the outer ends of the members for connecting them to adjacent sections of a pipe string; c. pairs of male and female spline elements cooperably disposed respectively on the outer and inner members to form a nonrotating, longitudinally slidable connection between said members and to define a continuous annular bearing race therebetween; d. a pair of angularly spaced, elongate, generally rectangular openings in the wall of said outer member registering with said female spline elements and adapted to removably receive said male spline elements; e. flange elements extending from the sides and ends of said male spline elements to overlie the related edges of said openings; f. fastening means releasably securing said flanges to said outer member about said openings; and g. bearing means operably disposed in said bearing race.
 2. An extensible coupling according to claim 1 including a sealing assembly positioned in sealing relation between said coupling members below said slidable connection.
 3. An extensible coupling for well pipe strings comprising: a. telescopically engaged inner and outer tubular members; b. means carried by the outer ends of the members for connecting them to adjacent sections of a pipe string; c. an elongate, generally rectangular recess in the exterior of said inner member defining a female spline; d. an elongate, generally rectangular opening in the wall of the outer member registering with said recess; e. a closure plate removably mounted in said opening and corresponding in shape thereto; f. means for releasably securing said plate about said opening; g. an elongate male spline carried on the inner face of said closure plate to be nonrotatively slidably received in said recess; h. a bearing race defined between the sides of said male spline and the adjacent walls of said recess; and i. ball bearing means operably disposed in said bearing race; said closure plate having bolt flanges symmetrically disposed along its side edges and opposite ends to permit turning said male splines end-for-end in said openings while maintaining said defined bearing race between said spline element. 